Description of data in 'anscombe.dat'

From Anscombe FJ 1973 Graphs in statistical analysis
The American Statistician, 27, 17-21.

used on pages 4-5 in text 
Modern Regression Analysis, author Ryan TP, Wiley New York 1997.

There are 4 data sets in all.
The x values are common in the 1st 3 datasets.

Variables   

x1_x3     x in 1st 3 datasets
y1        y in 1st dataset
y2        y in 2nd dataset
y3        y in 3rd dataset
x4        x in 4th dataset
y4        y in 4th dataset

Anscombe showed that completely different graphs can correspond
to the same regression equation and summary statistics. In 
particular, he showed that the need for a quadratic term in X
can correspond to the same regression equation as a graph,
which clearly indicates that a linear term is sufficient.

Exercises

Plot each of the four datasets. Then determine the prediction
equation Yhat = beta_0_hat + b_1_hat X. Do your results suggest that
regression data should be plotted before any computations
are performed?